Beam collimation using multiple coupled elements

Abstract

An electrically pumped, distributed feedback laser having all side surfaces of the active laser medium cleaved and a periodic structure at a 45° angle to all of the cleaved surfaces. Current confining channels restrict pumping current to selected regions of the active laser medium to provide sufficient feedback such that two parallel filamentary areas of the active medium lase. By having multiple lasing filaments the divergence of the output beam in the direction of the width of the filaments is reduced by a factor proportional to the number of filamentary lasing areas.

What is claimed is: 
     
       1. A heterojunction diode laser comprising: a light waveguide layer of semiconductor material, said waveguide layer being sandwiched between first and second adjacent layers of semiconductor material with at least one of said adjacent layers being of a different material than the material of said waveguide layer, one of said adjacent layers being of a different conductivity type than the conductivity type of said waveguide layer such that a PN junction is formed therebetween,   means for electrically pumping at least two spaced parallel regions of said waveguide layers so that light photons are generated in and travel throughout said waveguide layer,   means for substantially totally internally reflecting said light photons so that at least a portion of said light photons follow a path within said waveguide layer which path has sections which are in alignment with said spaced parallel regions of said waveguide layer, and   a periodic structure within said diode laser, said periodic structure having a plurality of parallel teeth which are oriented such that their projections are perpendicular to said spaced parallel regions such that said portion of said light photons will be reinforced in a coherent manner thereby providing the feedback necessary to produce two parallel output light beams.   
     
     
       2. The heterojunction diode laser of Claim 1 wherein said waveguide layer is GaAs and said at least one of said adjacent layers is GaAlAs. 
     
     
       3. The heterojunction diode laser of Claim 1 wherein said means for substantially totally internally reflecting said light photons is the cleaved surfaces of said light waveguide layer. 
     
     
       4. The heterojunction diode laser of Claim 3 wherein said teeth make a 45° angle to all of said cleaved surfaces. 
     
     
       5. A heterojunction laser comprising: a light waveguide layer of semiconductor material, said waveguide layer being sandwiched between first and second adjacent layers of semiconductor material with at least one of said adjacent layers being of a different material than the material of said waveguide layer, one of said adjacent layers being of a different conductivity type than the conductivity type of said waveguide layer such that a PN junction is formed therebetween,   means for electrically pumping at least two spaced parallel regions of said waveguide layers so that light photons are generated in and travel throughout said waveguide layer,   means for substantially totally internally reflecting said light photons so that at least a portion of said light photons follow a path within said waveguide layer which path has sections which are in alignment with said spaced parallel regions of said waveguide layer, and   a periodic structure within said diode laser, said periodic structure having a plurality of parallel corrugations which are oriented such that their projections are perpendicular to said spaced parallel regions, said corrugations having a spacing therebetween equal to an integer number of wavelengths of said light photons such that said portion of said light photons will be reinforced in a coherent manner thereby providing the feedback necessary to produce two parallel output light beams perpendicular to the plane of said PN junction.   
     
     
       6. The heterojunction diode laser of Claim 5 wherein said means for substantially totally internally reflecting said light photons is the cleaved surfaces of said light waveguide layer. 
     
     
       7. The heterojunction diode laser of Claim 5 wherein said means for electrically pumping said at least two spaced parallel regions of said waveguide layer are elongated portions of one of said adjacent layers with said elongated portions surrounded by highly electrically resistive portions of said one of said adjacent layers. 
     
     
       8. The heterojunction diode laser of Claim 3 wherein said means for electrically pumping said at least two spaced parallel regions of said waveguide layer are elongated portions of one of said adjacent layers with said elongated portions surrounded by highly electrically resistive portions of said one of said adjacent layers. 
     
     
       9. A heterojunction diode laser comprising: a light waveguide layer of semiconductor material, the side surfaces of said waveguide layer being cleaved and said layer being sandwiched between first and second adjacent layers of semiconductor material with at least one of said adjacent layers being of a different material than the material of said waveguide layer, one of said adjacent layers being of a different conductivity type than the conductivity type of said waveguide layer such that a PN junction is formed therebetween,   means for electrically pumping at least two spaced parallel regions of said waveguide layer oriented at a 45° angle to said surfaces of said waveguide layer so that light photons are generated in and travel throughout said waveguide layer, said means including means for restricting pump current flow to only said at least two spaced regions, and   a periodic structure within said diode laser, said periodic structure having a plurality of parallel teeth which are oriented such that their projections are perpendicular to the longitudinal dimension of said spaced parallel regions, said teeth having a spacing therebetween equal to an integer number of said light photons such that said light photons are reinforced in a coherent manner thereby providing two parallel output light beams perpendicular to the plane of said PN junction.